Reef Fish Assemblages in the Western Arabian Gulf: A Geographically Isolated Population in an Extreme Environment

Fishes were surveyed on coral reefs in the western Arabian Gulf seasonally over a 2-year period. The total number of species found equaled or exceeded previous studies in the Gulf, but was low compared to other Indo-Pacific areas, suggesting fish diversity to be limited by either geographic isolation or by stressful environmental conditions. Numbers of species and individuals varied according to nearshore-offshore location, level on the reef, and season. Greater numbers offish species and individuals consistently occurred offshore and at greater depths on the reefs. Populations increased in summer–fall and decreased in late winter–early spring at most locations, inversely related with annual temperature cycles. The summer increases in fish numbers occurred in all size classes and were not due to seasonal juvenile recruitment. The seasonal changes in fish numbers suggest movement of reef fishes from nearshore reefs in summer to offshore reefs in winter, possibly to avoid greater physical stresses in inshore areas.